The invention relates to on a method of and an apparatus for controlling a quantity of an explosive gas mixture in a treatment chamber for thermal deburring of workpieces. Such a method for eliminating thin burrs and unwanted thin edges and projections on workpieces having considerably thicker cross sections is known from the DE-PS No. 17 52 440. The method is based on the fact that a workpiece to be treated is exposed to a sudden brief heating action within a defined space which is sealed in a pressuretight manner, which heating action is produced by ignition of a quantity of a combustible gas mixture, which quantity is determined beforehand. Aside from the surface-to-volume ratio between the burr and the basic body of the workpiece, as well as the heat conductivity of the work material, it is important and decisive for the results of the thermal workpiece treatment that the degree of admission of the treatment chamber be as high and as uniform as possible, i.e. many small workpieces or a large workpiece which just fits into the chamber must be inserted. With respect to workpiece treatment, only the sum of all surfaces is important. The more surfaces are located in the chamber, the more the heat quantity is distributed.
The heat shock is produced by burning off a combustible gas-oxygen mixture, wherein hydrogen or natural gas and methane, respectively, are used as combustible gas. Two influencing variables are available for controlling the deburring process, namely the gas quantity in the combustion space and the mixture ratio of the gas components. These influencing variables determine the quantity of energy and the temperature. As a rule, metals are deburred with an oxygen surplus, since otherwise only melting, but not a combustion, of the burrs would be effected.
Known systems or apparatus thermal deburring are charged by hand, wherein the workpieces are either placed directly on the closing plate of the treatment chamber or are inserted in a pot or a workpiece holder in the chamber. In order to ensure the most economical operation, the workpieces are sorted beforehand according to size, i.e. workpiece batches with at least approximately the same volumes are combined and treated one after the other. In this way it is possible to maintain the quantity of gas mixture which is determined for the respective batch and adjusted in a metering device of the system until a batch with a different volume is ready to be treated. It is costly and time-consuming to determine and adjust the quantity of gas mixture required for deburring workpieces of different volumes; for this reason, difficulties are encountered in the linking of thermal deburring systems with other workpiece treatment machines in production lines operated in a clocked manner when workpieces having different dimensions are delivered on a conveying device, e.g. a conveyor belt, in an undifferentiated manner.